In recent years, catalytic converters have been used extensively in treating exhaust gases from internal combustion engines. This is particularly true in the area of internal combustion engines used in automotive vehicles.
When an automotive vehicle is equipped with a catalytic converter, it is necessary for the operator of the vehicle to use unleaded gasoline as the fuel. This requirement is caused by the fact that a leaded gasoline will deteriorate the activity of the catalytic converter. More particularly, the lead used in a leaded fuel acts as a poison for most materials used as catalysts for motor vehicles. Lead will deactivate catalysts formed from materials such as platinum, palladium, ruthenium, rhodium, iridium, etc. Once deactivated, these catalysts are no longer effective in treatment of the exhaust gases.
Some operators of vehicles which are required to be operated on unleaded fuel only will, in fact, use a leaded fuel in the vehicle. Basically, the reason for using a leaded fuel is an economic one since leaded fuels are generally several cents per gallon less than unleaded fuels.
Thus, for those manufacturers who equip internal combustion engines with catalytic exhaust treatment devices, it is important to know whether or not the internal combustion engine has used leaded fuel during its operation. For example, if the operator of a catalytically equipped automobile returns the vehicle under warranty and requests a new catalytic converter to replace a defective one, it is important to determine if the catalytic converter was rendered ineffective because the user burned leaded fuel during operation of the vehicle. If the operator of the vehicle has been misfueling the vehicle, that is, putting leaded fuel in the vehicle when unleaded fuel is required, he then is solely responsible for the damage to the catalytic converter. In such an instance, the operator of the vehicle must stand the cost of replacement of the very expensive catalytic converter, rather than the company who manufactures the same.
It is, therefore, a principal object of this invention to provide a method of determining if an internal combustion engine has been operated by burning a leaded fuel therein, which method is simple and efficient in operation and positive in results.
It is still another object of this invention to provide a method of determining if an internal combustion engine has been operated by burning a leaded fuel, which method gives an integrated overall value for the amount of leaded fuel which has been burned in the engine.
A prior art search was conducted on the subject matter of this specification in the public search room of the U.S. Patent Office. This search resulted in the citation of six patents, none of which resembles the method set forth in this specification. The patents cited and the reasons why they are not germane are set forth below.
U.S. Pat. No. 2,787,903 is directed primarily to separating a corrosive gas from a gas sample to be analyzed. The device disclosed is based on the permeability of gases through a material and it does not measure an integrated exposure.
U.S. Pat. No. 3,174,325 is directed to improvements in instruments for qualitatively analyzing gases. The device disclosed detects gases which are desorbed selectively from the surface of a porous solid as the temperature of that solid is raised.
U.S. Pat. No. 3,431,771 is directed to an instrument used for qualitative and quantitative detection of a gas in a mixture of various gases. The gas under test is admitted to the test device in a mixture of gases and is selectively absorbed by an absorbant after passing through a microporous element of accurately controlled porosity. A device is provided for measuring electrical resistance changes in the absorbant whereby the properties of the absorbable gas may be indicated.
U.S. Pat. No. 3,941,566 is directed to a device for determining carbon activity through a pressure measurement. The device is fairly complex and it is designed to measure instantaneous activity of carbon in molten metal.
U.S. Pat. No. 4,143,316 is directed to a diffusion type hydrogen meter for improving the sensitivity and response time for the measurement of hydrogen in liquid sodium. This device is based on the diffusion of hydrogen through a solid and measures the instantaneous hydrogen concentration in liquid sodium.
U.S. Pat. No. 4,192,175 discloses a process and apparatus for measurement of diffusable hydrogen within a metal. This device may be used to measure hydrogen in steel.